Real-Life Math -- Solution
You're a pedigree analyst doing research on a horse's pedigree. You want to know the pedigree of the stallion. How many ancestors will you have to look at in each generation?
1. How many ancestors are in the stallion's sixth generation?
Each time you go back a generation, the number of ancestors doubles.
1 generation: 2 ancestors
2 generations: 2 ancestors x 2 = 4 ancestors
3 generations: 4 ancestors x 2 = 8 ancestors
4 generations: 8 ancestors x 2 = 16 ancestors
5 generations: 16 ancestors x 2 = 32 ancestors
6 generations: 32 ancestors x 2 = 64 ancestors
In the sixth generation, the horse has 64 ancestors.
2. How about the seventh?
6 generations: 64 ancestors
7 generations: 64 ancestors x 2 = 128
In the seventh generation, the horse has 128 ancestors.
Thoroughbreds have been traced back 25 to 30 generations. "If you counted that up, you'd find that each horse has something like 68 billion ancestors," says Les Brinsfield.
Of course, there never were that many thoroughbred horses. How can that be? Many of the horses are duplicates, or occur many times within one horse's chart. That fact is key in breeding horses.